A. Field of the Invention
The device of the present invention generally relates to a new and improved safety treatment for the ends of W-beam guardrails; and more particularly, to a new and improved guardrail extruder terminal that is mounted at the end of a W-beam guardrail for dissipating impact energy of a car colliding with the end of the W-beam guardrail in an accident.
B. Description of the Prior Art
Along most highways there are hazards that can be a substantial danger to drivers of automobiles if the automobiles were to leave the highway. To prevent accidents due to vehicles leaving a highway, guardrails are provided. Guardrails must be installed such that the terminal end of the guardrail facing the flow of traffic is not a hazard. Early guardrails had no proper termination at the ends, and it was not uncommon for impacting vehicles to become impaled on the guardrail causing intense deceleration of the vehicle and severe injury to the occupants. In some reported cases, the guardrail penetrated directly, into the occupant compartment of the vehicle fatally injuring the occupants.
Upon recognition of the problem of proper guardrail termination, guardrail designs were developed that used box beams and W-beams that allow tapering of the end of the guardrail into the ground providing a ramp and eliminating any spearing effect. While these end treatments successfully removed the danger of the vehicle being penetrated in a head-on collision, it was discovered that these end treatments could induce launching of the vehicle causing it to become airborne for a considerable distance with the possibility of roll over.
In search for better end treatments, improved end treatments such as break away cable terminals (BCT), vehicle attenuating terminals (VAT), and the Sentre end treatment were developed. These end treatments do not induce the dangerous vaulting and roll over of vehicles. The BCT end treatment is designed to cause a W-beam guardrail to buckle out of the way of an impacting vehicle. Since this design relies on dynamic buckling of the W-beam, it is sensitive to many installation details such as barrier flare rate and end off-set. Consequently, this design has not had a favorable service history.
The VAT safety treatment consists of overlapped guardrail sections that have a series of closely spaced slots. The guardrail segments are attached by bolts extending through the slots. When a vehicle impacts the end of this barrier, the bolts are forced to tear through the W-beam from one slot to the next. As a result, W-beam segments are cut into several long ribbons as an impacting vehicle is decelerated. The VAT safety treatment has no field service record, but it is believed that this system is too costly for wide spread implementation.
The Sentre end treatment is constructed from a series of break away steel guardrail posts and fragile plastic containers. Impacting vehicles are decelerated as the guardrail posts are broken and sand bags in the plastic containers are impacted. A cable is used to guide vehicles away from the guardrail during impact. This system is very expensive, and due to this expense, has not gained wide acceptance.
It would be desirable to develop an end treatment that can be used at virtually any end of a guardrail as a means of attenuating head on impacts as well as for providing anchorage for impacts to the sides of the barrier. It is also desirable that such an end treatment be easily installed and serviced and inexpensive to manufacture.